Numerous devices which are useful for the automated assembly of products have been successfully used for many years. In each instance, automated assembly devices have been employed with a view toward increasing the efficiencies and accuracies of the methods, procedures and processes which are followed during the manufacture and the assembly of a completed product. Indeed, the vast majority of consumer products are now manufactured on assembly lines which incorporate automated assembly devices.
It is easy to appreciate that as the complexity of a manufactured product increases, there may also be a commensurate increase in the complexity of the machines that are required to manufacture the product. This is particularly so where the component parts are delicate or fragile and precision is important. For example, many products require the precise positioning and assembly of extremely small and light weight components in their manufacture. More specifically, these operations require precision in both the linear translational movement of the component into position and in the force with which the component is moved and assembled with other components. Rotational movements of the component can often be acceptably accomplished with a lower degree of precision. For instance, some operations require only that rotational movements of approximately 90.degree. or 180.degree. be accomplished.
Furthermore, for quality control purposes it is often necessary that there be some way to obtain a real time check on the precision with which the component was positioned during the assembly of the product. Where very small, fragile or light weight components are being used in the manufacturing process, and where either very light forces or normal forces are required for the assembly of these components these considerations become very important.
Of the known devices which are typically used for automated assembly, systems incorporating solenoids can be quite precise. However, the forces which solenoids impose on components during their handling of the component can be destructive to the component or be otherwise unacceptable. One other general type device, the well-known stepper motor, also deserves some mention. Generally, stepper-motor systems can be spatially precise in their operation, and the forces which they generate can be effectively controlled. Stepper-motors, however, are bulky items and do not have good light force generation characteristics. In some manufacturing procedures these factors can be of significant disadvantage. Pneumatic devices are not known for performing with high precision, primarily because of their damping characteristics. However, they are sometimes suitable for achieving some modes of motion in a precision device. An example of this is in a transporter device in which the only required rotational movement of the assembly component is a rotation of approximately 90.degree. or 180.degree. without high precision. Such a need might arise in the assembly of a component which incorporates self aligning features, or in the placing of a component on a conveyor belt for packaging. Consequently, the present invention has recognized that an electronically operated system can be effective for the precise placement of a product component during assembly without encountering the force and spatial problems confronted by the above discussed types of systems. The present invention also recognizes that, in some applications of a precision transporter apparatus, the rotational mode of motion can be adequately and economically accomplished by the use of a pneumatically driven rotary actuator. More specifically, the present invention recognizes that a voice coil linear motor can be applied for these purposes, and that a pneumatic rotary actuator can be coupled with the voice coil linear motor, to accomplish certain high tolerance rotational motion.
While U.S. Pat. No. 4,498,023 which issued to Stout for an invention entitled "Voice Coil Linear Motor with Integral Capacitor" addresses some of the issues which are of concern to the present invention, it does not address all of the important issues. For example, the present invention is concerned with maintaining precise concentricity between the parts of the device as they move relative to each other. Stout does not precisely address this problem. Further, the present invention envisions a compact configuration for the device which may not be attainable with the cylindrical coil disclosed for the Stout device. Additionally, due to the suggested magnet strengths, a device such as the one disclosed in U.S. Pat. No. 4,498,023 can expect to have heat generation problems which drastically effect the proposed sensors accuracy thereby rendering the device ineffective.
The present invention also recognizes there are instances when it is important that a work product be both precisely moved in a translational motion, and oriented rotationally, but with a higher degree of tolerance. Further, there are instances when it is necessary for the work product to be rotated to join the work product to another component such as when it is necessary to thread or screw one component into another.
In addition to the advantages alluded to above, an electronic system has other characteristics which can be advantageous for a device which is to be used in the automated assembly of an end product. For example, some electronic system can rather easily lend itself to compact configurations. Further, an electronic system is responsive and can be configured to provide signals which can be used to monitor and control the operation of the system.
It has also been recognized that many components are relatively fragile, and that such components should not be subjected to compressive forces by a gripping means. Finally, it has been recognized that it can be advantageous to have a gripping means which can grip a variety of different shapes and release them with great precision, without imparting directional forces such as those which can result from typical grasping mechanisms.
In light of the above, it is an object of the present invention to provide a device for moving, inspecting and positioning a component in an automated assembly operation which is capable of picking-up, transporting and depositing fragile and light weight components. It is another object of the present invention to provide a device for moving and positioning a component in an automated assembly operation which has effective control of either extremely small forces or normal forces, and which can control such forces within a relatively fast response time. Yet another object of the present invention is to provide a device which can transport assembly components with minimal bounce (i.e. little, if any, changes in linear direction) at the end of a component placement operation. Still another object of the present invention is to provide a device for moving, inspecting and positioning a component in an automated assembly operation which can be effectively monitored for real time verification of operational accuracy. Yet another object of the present invention is to provide a device for moving and positioning a component in an automated assembly operation wherein there is appropriate control over both the translational and rotational positioning of the work piece being transported, and which can grip a component without applying compressive forces on the component, and without imparting directional forces on the released component. Another object of the present invention is to provide an automated assembly device which is relatively simple to use, is relatively easy to manufacture and is comparatively cost effective.